The diagnostic performance of a magnetic resonance imaging (MRI) apparatus varies directly with the number of detectors used to detect the available nuclear magnetic resonance (NMR) signals emanating from an object. Yet conventional systems have a finite limit on the number of detectors. The finite limit is related to cabling connections between detectors and processing apparatus (e.g., scanner, computer). Consider that conventional systems with multiple detectors may include several miles of cabling connections. This increases the cost, space requirements, and weight of an MRI apparatus. This also produces the limitation concerning the number of detectors possible in conventional systems.
Since cabling connections between detectors and other MRI apparatus elements are a limiting factor, attempts have been made to connect detectors to other MRI apparatus elements using wireless techniques. The techniques include, for example, time multiplexed optical transmission, digital wireless transmission, and so on. However, time multiplexed optical transmission still experiences a limit on the maximum number of detectors that can be supported. Additionally, digital wireless transmission solutions have suffered from bandwidth limitations, have required complex digital conversion equipment, and have required an unacceptable amount of power. Therefore, research into additional wireless techniques for connecting detector coils to MRI apparatus elements is ongoing.
Recall that MRI apparatus use coil sensors to detect NMR signals emanating from an object. Recall also that these NMR signals are relatively weak compared to RF noise in a general environment. Therefore, MRI apparatus are generally located in rooms that are shielded by a Faraday cage. While the Faraday cage can limit the intrusion of RF noise from outside the room, it cannot address RF noise generated inside the room, in the MRI environment. Clearly the detector coils must be located in the room because the relatively weak NMR signals cannot escape the room. Therefore, electronics, circuits, cabling, and so on located inside the room have conventionally been shielded to limit the RF noise they can introduce into the room. However, this shielding adds yet more mass, volume, and expense to an MRI apparatus.
RF signals transmitted wirelessly from a detector coil may be more powerful than NMR signals transmitted from a resonating body. Thus, if RF signals are transmitted while NMR signals are being detected, detecting the NMR signals may be compromised. Therefore, using remote devices like wireless transmitters associated with detector coils has been limited, if even possible at all, because signals and noise associated with remote devices have interfered with detecting the NMR broadcast by the resonating body. To be practical, wireless transmission of signals from a detector coil to an MRI apparatus element must not interfere with the NMR signals being received by a detector coil. Additionally, circuitry to control wireless transmitters must not produce noise that interferes with detecting NMR signals.
Wireless transmitters associated with detector coils seem to provide a path to overcome mass, volume, and expense issues associated with cabling connections. And yet wireless transmitters need to be controlled by circuits that traditionally have introduced unacceptable RF noise into the room. Parameters that need to be controlled for wireless transmitters associated with detector coils include, for example, channel identification, channel spacing, power settings, and so on. Conventionally, a tuning logic may have configured a typical transmitter associated with a remote magnetic coil sensor. But this tuning logic may have produced electromagnetic (e.g., RF) noise while controlling the transmitter. This electromagnetic noise may have interfered with detecting relatively weaker NMR signals.
Previous efforts to mitigate these issues have included microcontroller governed MR devices. Conventional microcontrollers have been used to control the frequency of a multiplexing system and controlled digital transmissions. These conventional microcontroller based systems used volatile memory and thus required direct programming at each power up. This may have created configuration and interference issues. The volatile memory and/or microcontroller may have been continuously clocked and this may have continually produced RF noise. Another conventional microcontroller based system included an implantable detector tuning control that controlled a single detector but did not mitigate the issues described above.